Shooting Prone with high power scopes is normally where it is worse because your belly is on the ground and this causes your diaphragm to react to your heart beat and move you up and down in time with your heart beat.
As suggested, lower power will at least minimize the appearance of movement, Sometimes this
lets you concentrate on trigger control and not so much on your heart beat and in some cases shoot better.
When I shot prone matches I found out that if I did not eat until after the match, I had better scores. (Your heart beats faster and harder when trying to digest food) Also once I figured out the wind and mirage if shooting a match where scopes were allowed, I lowered the power of the scope where all of these problems didn't seem to bad and just concentrated on hold and trigger control. It will mess with your mind if you let it. As stated you can calm it to some extent but you cant stop it.
The other way that helped was to start squeezing just after you heart beat, and hopefully the trigger would break before the next heart beat. You have to practice this or you will end up punching the trigger and we all know where that leads.
J E CUSTOM